Manufacture of chlorine dioxide from an alkali metal chlorate and an alkali metal nitrite



MANUFACTURE OF CHLORINE DIOXIDE FROM AN ALKALI METAL CHLORATE AND AN AL-KALI METAL NITRITE Souren Z. Avedikian, Plaintield, N. J.

No Drawing. Original application January 36, 1956, Se-

rial No. 562,017, new Patent 'No. 2,834,649, dated May 13, 1958. Dividedand this application April 23, 1958, Serial No. 739,245

4 Claims. (Cl. 23-152) This invention relates to a composition forpreparing chlorine dioxide and to the method of preparing chlorinedioxide from said composition.

This application is a division of Ser. No. 562,017, new Patent No.2,834,649.

Liquid chlorine dioxide is of particular interest in the bleaching ofwood pulp since it does not attack cellulosic fibers. However, chlorinedioxide gas is not a stable compound so that it must be generated at theplace of use. The danger of explosion is avoided by mixing chlorinedioxide with air or other inert gas to obtain a mixture containing lessthan percent chlorine dioxide by volume.

Also relatively concentrated aqueous solutions of chlorine dioxide arestable at room temperature for long periods of time.

There are many methods for preparing chlorine dioxide but they all areexpensive procedures or cumbersome as to utilization of time and factoryspace.

It is an object of this invention to produce chlorine dioxide moreinexpensively than ever before.

It is another object to produce chlorine dioxide conveniently andreadily.

It is a further object to produce chlorine dioxide with a minimum ofapparatus.

It is still another object to produce chlorine dioxide by a processhaving a by-product of ready sale.

These and other objects of this invention will become apparent uponreading the following descriptive disclosure.

According to this invention a stable mixture of salts is prepared whichreadily yields chlorine dioxide upon treatment with acid.

The stable mixture consists preferably of alkali metal chlorate andalkali metal nitrite, for example NaClO; and NaNO The chlorate nitritemixture is preferably an intimate finely ground dry mixture of the twosalts, each salt being finely ground preferably before the mixing step.Separate strong aqueous solutions of these two salts, viz, F, sodiumchlorate and sodium nitrite are operable to release chlorine dioxideupon mixing followed by acid treatment. Furthermore the nitrite andchlorate may be in the form of a single stable aqueous mixture prior toacidification. Thus the operable saline mixtures of this inventien maybe dry or wet with water. These mixtures are stable for long periods oftime, for example, several days or weeks so that they may be preparedlong before need for their use.

Patented Dec. 30, 1958 ice Upon use the dry powder mixture is treatedwith dilute aqueous acid preferably with a dilute mineral acid such assulfuric acid. However, in the case of the aqueous concentrated saltsolutions these are treated with eoncentrated mineral acids. In eithercase chlorine dioxide is formed in abundant quantity. The chlorinedioxide so formed is swept out of the reaction vessel by an inert gaspreferably air to give a mixture of 10 percent or less of chlorinedioxide.

The gaseous chlorine dioxide prepared by thisinvention is generatedsmoothly and the gas is uncontaminated with other gases, for examplesulfur dioxide, harmful to the subsequent use of chlorine dioxide as ableaching gas.

The temperature used to liberate chlorine dioxide from its mixture maybe from 40 C. to 80 C. bu preferably 60 C. to C. is used.

The following example illustrates this invention.

Example The chemical reaction for this salt mixture is expressed by thefollowing equation:

In this invention potassium chlorate or calcium chlorate may be used inplace of sodium chlorate, so that clearly this invention is not limitedto its illustrative embodiments described herein.

I claim:

1. A dry chemical composition of matter for liberating pure chlorinedioxide upon treatment with aqueous acid solution consisting of twomoles of finely divlded sodium chlorate mixed with one mole of finelydivided sodium nitrite.

2. A wet composition of matter for liberating chlorine dioxide uponacidification consisting of two moles of an aqueous concentratedsolution of alkali metal chlorate admixed with one mole of aconcentrated solution of alkali metal nitrite.

3. The method of preparing chlorine dioxide consisting of adding a drymixture of a salt consisting of two moles of finely divided sodiumchlorate mixed with one mole of finely divided sodium nitrite to asuitable amount of aqueous acid solution to liberate chlorine dioxide.

4. The method of claim 3 wherein the acid solution is sulfuric acidmaintained at 40 C. to C.

References Cited in the file of this patent UNITED STATES PATENTS2,309,457 Hutchinson et al. Jan. 26, 1943 2,317,443 Cunningham Apr. 27,1943 2,335,808 Soule Nov. 30, 1943 2,338,268 Stossel et al. Jan. 4, 19442,451,826 Haller Oct. 19, 1948 2,481,854 MacMahon Sept. 13, 19492,482,891 Aston Sept. 27, 1949 2,484,401 Day et al. Oct. 11, 1949

3. THE METHOD OF PREPARING CHLORIDE DIOXIDE CONSISTING OF ADDING A DRYMIXTURE OF A SALT CONSISTING OF TWO MOLES OF FINELY DIVIDED SODIUMCHLORATE MIXED WITH ONE MOLE OF FINELY DIVIDED SODIUM NITRITE TO ASUITABLE AMOUNT OF AQUEOUS ACID SOLUTION TO LIBERATE CHLORINE DIOXIDE.